1. Field of the Invention
This invention relates in general to vibrational energy isolators, and in particular, wire rope isolators. More specifically, but without restriction to the particular embodiment hereinafter described in accordance with the best mode of practice, this invention relates to wire rope vibration isolators utilizing mounting blocks that employ dowel pins to mechanically engage wire ropes passed through lateral holes in the mounting blocks into locking contact with the blocks and the method of assembling such isolators.
2. Background of the Prior Art
Many operations require energy absorption devices to divert damaging vibrational energy away from shock-sensitive equipment and machinery. Shipboard electronics and navigational equipment, pumps, generators and compressors, chemical processing equipment, avionics, process piping and various other industries utilize energy dampers to prevent damage and premature wear to equipment vital to daily operations. The most basic energy absorption devices employ simple internal machinery, like pistons and springs, to harmlessly consume vibrational or kinetic energy thereby insulating shock-sensitive equipment secured to the device from potential damage caused by the unwanted vibrational energy. For example, the common automotive shock absorber, a member of the class of these devices, uses the shock force caused by driving on an uneven surface to move an internal piston which in turn decreases the total amount of energy of the system.
A common type of energy-absorbing restraint is the wire rope isolator. Most isolators of this class utilize a multi-strand wire rope that has been manipulated into a geometric shape. Particular geometric configurations impart the rope with elastic spring-like qualities which allow the wire rope to flex and contract when subject to dynamic displacement. The undulation of the rope consumes vibrational energy.
Most wire rope isolators currently utilized in industrial applications shape the wire rope into a coil or helix, although other configurations, such as saddles, are possible. The desired geometry of the wire rope is attained, in most instances, by threading the wire rope through hollow cylindrical members, channels and the like drilled into two or more entrapment members or mounting blocks. To maintain the wire cable in a helical formation, some devices secure the mounting blocks together with threaded fasteners. Examples of these types of isolators are illustrated in U.S. Pat. No. 3,596,865 issued to C. Camossi, U.S. Pat. No. 4,783,038 issued to C. L. Gilbert, et al., U.S. Pat. No. 5,062,507 issued to A. Roche. In addition, the isolator designs illustrated in the Loziuk patents, U.S. Pat. Nos. 5,441,243, 5,522,585 and 5,791,636, all of which suggest securing the two mounting blocks together with a threaded fastening means like a bolt which in turn maintains the helical formation of the wire rope. While this type of isolator has its advantages, there is a possibility that the threaded fasteners may become loose at some time.
The vibration isolator proposed by R. E. Belfield et al., U.S. Pat. No. 4,190,227 employs a method whereby the wire cable coil is molded in a retainer block which is formed from a thermoplastic material such as polyvinyl chloride or polystyrene. This proposal also has its disadvantages. It may fail under heavy loads or high temperatures. In addition, the bonded interface between the thermoplastic material and the wire cable may fail due to cyclic fatigue.
The wire rope isolator illustrated in U.S. Pat. No. 5,549,285 issued to Collins suggests that the wire rope configuration can be maintained and secured by a crimp. This type of isolator requires that the mounting blocks be forged from a malleable material. The wire rope cable is threaded through a series of lateral holes contained in the mounting blocks forming a helix. A force is then applied to at least one of the mounting blocks at a point where the wire rope is positioned so as to plastically deform the mounting block around the wire rope into locking contact. This design, however, is ill-suited for use with wire cables having large diameters. Wire ropes with large diameters require mounting blocks of substantial mass. Crimping a substantially thick mounting block around an equally dense wire cable would require a tremendous amount of force which in turn would result in an overall reduction of the integrity of the mounting block.
The other wire rope isolators described herein that use fasteners to secure the wire rope in place are also ill-suited in applications using wire ropes with significant diameters. As such, the production of large-scale isolators is limited. Accordingly, there continues to be a need for wire rope isolators constructed with wire ropes having relatively great diameters assembled without the use of any mechanical fasteners.
The present invention consists of a wire rope isolator that employs dowel pins to mechanically stake and/or engage the wire rope cable into locking contact with the mounting blocks. The dowel pins are forged of a material having a harder consistency than the material composing the mounting block and wire rope. The end of the dowel pin not engaging the wire rope is pressed flush to the outer surface of the mounting block. A simple wire rope isolator can be assembled by passing a wire cable through hollow cylindrical members, channels and the like contained in two or more mounting blocks so as to manipulate the wire rope into a geometric shape which imparts the wire rope with elastic, spring-like qualities. When the assembled isolator is connected to shock-sensitive machinery and/or equipment, the isolator insulates said machinery and/or equipment by deflecting potentially damaging vibrational energy away from the equipment when the mechanical system is subject to a dynamic load. In particular, the wire rope flexes and contracts causing the mounting blocks to move relative to each other to dissipate vibrational energy.
In a preferred embodiment, the ends of the dowel pins engaging the wire cable can be a wedge so as to facilitate the staking process. This goal is also achieved by including pilot holes in the mounting blocks that are perpendicular to the lateral holes in which the wire rope is situated. The dowel pin is driven directly into the wire rope avoiding the need to penetrate the surface of the mounting block. In accordance with a further aspect of this invention, the dowel pins used can be forged from hard steel while the mounting block and isolator are made from aluminum.
It is, therefore, an object of this present invention to improve energy absorption devices.
Another object of this invention is to improve wire rope vibration isolators for use in industrial applications.
It is a further object of the present invention to assemble a wire rope vibration isolator without the use of any mechanical fasteners.
Still another object of the present invention is to assemble a wire rope isolator that uses a wire cable having a diameter greater than the diameter of conventional wire cables currently available in industrial applications without compromising the integrity of the mounting block in which the cable is housed.
It is yet a further objective of the present invention to utilize all metal components in a wire rope vibration isolator so that the isolator may function under extreme operating conditions such as temperature and load.
Yet still another object of the present invention is to avoid a bonded chemical interface between the block member and the wire rope.
An additional object of the present invention to eliminate costly machining operations associated with securing retainer plates to the wire coils of a wire rope isolator.
Yet a further object of the present invention is to reduce the number of parts required to assemble a wire rope isolator for industrial applications.
Still yet another object of the present invention is to decrease the number of steps required for assembling a variety of sizes of wire rope isolators.
These and other objectives are attained in accordance with the present invention.